Random: Variety is the spice of life

Type in the following example:

// Declare and initialize your variables!

float r = 100;

float g = 150;

float b = 200;

float a = 200;

float diam = 20;

float x = 100;

float y = 100;

void setup() {

  size(480, 270);

  background(255);

}

void draw() {

  // Use those variables to draw an ellipse

  stroke(0);

  // (Remember, the fourth argument for a color is transparency.

  fill(r, g, b, a);

  ellipse(x, y, diam, diam);

}

A dreary circle is just okay, but surely you could add fun with the random function. What if every time through draw(), you made a new circle, one with a random size, color, and position? The random() function allows you to do exactly that.

random() is a special kind of function. It's a function that returns a value . You have encountered this before. Think back to when you used the abs() function to calculate the absolute value of a number. The idea of a function that calculates a value and returns it will be explored later. For now, just let that idea sink in and start to marinate.

Unlike most of the functions you are comfortable with (ex: line(), ellipse(), and rect()) random() does not draw a color or shape on the screen. Instead, random() answers a question: it returns that answer to you. Here is a bit of dialogue to explain.

Me: Hey random, what's going on? Hope you're well...Listen, I was wondering, could you give me a random number between 1 and 100?

Random: Like, no problem dude. How about the number 63?

Me: That's awesome, really great, thank you. Ok, I'm off. Gotta draw a rectangle 63 pixels wide, OK?

Now, how would this sequence look in a more formal, Processing environment? The code below is the part of "me" and is played by the variable w.

float w = random(1, 100); // a random float between 1 and 100

rect(100, 100, w, 50);

The random() function requires two arguments and returns a random floating point number ranging from the first argument to the second. The second argument must be larger than the first for it to work properly. The function random() also works with one argument by assuming a range between zero and that argument.

In addition, random() only returns floating point numbers. This is why w is declared as a float . However, if you want a random integer, you can covert the result of the random function to an int. This is called CASTING (the process of converting one data type into another).

int w = int(random(1,100)); // a random integer between 1 and 100;

rect(100, 100, w, 50);

Exercise #1: You are ready to experiment with random(). Take the example code from the beginning of the page and DECLARE ONLY the variables at the top of the code. Then in draw INITIALIZE the variables and make each one random(). Run the code

Exercise #2:Take the alien creature ZOOG (code below). Add two more pieces of functionality to him.

New Feature #1 - Zoog will rise from below the screen and fly off into space (above the screen).

New Feature #2 - Zoog's eyes will be colored randomly as Zoog moves.

Exercise #3: Change the code for ZOOG so that he shakes left and right as he moves upward. Hint: This requires the use of random() in combination with zoogX.

zoogX = ______________________________;

You will need to save this code for next class. Save it as ZoogChapterFour

Last Random Exercise

#4 Can you code a circle to be in the middle of your screen and only move back and forth -2 and 2 pixels. Use random.